Many optical instruments require the use of a source lamp for producing radiation in a selected wavelength range. An example of such an instrument is an absorption photometer. An exemplary source lamp would comprise a substantially cylindrical glass or quartz envelope with a cylindrical protrusion, or "snout" extending from the side and defining the exit window. The actual radiation source within the lamp is very small, approximately one millimeter in diameter. When the lamp is installed within the instrument, the source must be exactly aligned with the optical axis of the instrument to provide maximum energy transfer. This adjustment may be made, although not without difficulty, when the instrument is assembled by the manufacturer. However, it is often necessary to change source lamps in the field, either because of failure or deterioration of the original lamp, or to substitute a lamp having a different wavelength emission range. This is when problems often arise due to the fact that the glass or quartz envelopes vary from lamp to lamp, resulting in corresponding variations in mechanical positioning and in the optical characteristics acting upon the source. Source lamp holders, in accordance with the prior art, are adjustable to compensate for these variations, but the adjustments are quite tedious and time-consuming and require the making of a number of separate but interrelated adjustments.
Still another problem which arises with prior art lamp holders is that the lamps tend to heat non-uniformly, thereby creating undesirable optical variations, especially during extended operation.
Accordingly, it is a primary object of the present invention to provide an improved, adjustable lamp holder for use with optical analytical instruments. Other objects are to provide such a holder wherein the heat distribution characteristics of the lamp are improved, wherein lamps are quickly and easily interchanged, and wherein the lamp position may be easily and quickly adjusted so that its radiation source is precisely aligned with the optical axis of the instrument. The manner in which the foregoing objects are achieved will be apparent from the following description and appended claims.